The present invention relates generally to a head and its manufacturing methods, and more particularly to control over a floatation amount of a head that floats above a disc surface. The present invention is suitable, for example, for a method for manufacturing a slider floating above a magnetic disc in a hard disc drive (“HDD”).
Available electronic information content has explosively increased with recent rapid technology development, as in the Internet. Accordingly, smaller and larger-capacity magnetic disc drives, typified by HDDs, have been increasingly demanded to store such a large amount of information. An increased number of data tracks per unit length (or TPI: Track per Inch), that is, a narrow track width, is essential to realize a smaller and larger-capacity HDD. In addition, the improved control over a floatation amount and an attitude of a slider mounted with a head is also required for writing data onto and reading data from a narrow track. The term “floatation amount” means, in this application, a floatation amount and an attitude during the floatation, unless otherwise specified. In particular, as the floatation amount of the slider has been decreased recently, the stable recording/reproducing operations have required control over the stable floatation amount. The head cannot achieve recording and reproducing, when its floatation amount is excessively large, since the magnetic field for use with recording and reproducing becomes small in proportion to the square of a distance. The excessively small floatation amount results in a crash (i.e., damage to a disc).
The slider has an air-bearing surface (“ABS”) that constitutes the floatation surface at a surface facing a disc, and it has been known that a shape or pattern of the ABS would stabilize the floatation amount. However, due to the residual stress generated at the time of processing a rear surface and the ABS of the slider, as well as the surface stress of the rear surface generated when the slider is bonded to a suspension, the ABS is warped like an ellipsoid, a paraboloid, or a hyperboloid, deviating from a desired shape. Therefore, the shape of the ABS should be measured, and then a correction or fine adjustment should be applied to the ABS when it is determined to be a bad shape.
One proposed method as a ABS-shape adjustment method has a laser irradiating onto the rear surface of the ABS to produce thermal stress and deform the rear surface minutely, thereby regulating a shape of the ABS, for example, as in Japanese Laid-Open Patent Application No. 6-84312. This adjustment method irradiates the laser to provide a crown or camber with a predicted deformed amount so that the ABS has a desired flat shape. Here, the crown is a swelling height on the slider in its longitudinal direction, whereas the camber (or often referred to as “cross-crown”) is a swelling height on the slider in its transverse direction.
Nevertheless, the above reference does not disclose a concrete method of setting a laser irradiation condition and a laser oscillation condition (both are generalized as “laser irradiation condition” in this application) so as to flatten the shape of the ABS, after the shape of the ABS is evaluated, i.e., when the measurement shows that a crown and/or camber are outside the permissible range. Therefore, a shape correction process requires skill, making difficult the correction and increasing the correction time. In particular, the crown and camber are interrelated with each other. For example, when the crown is inside the permissible range while the camber is outside the permissible range, an arbitrary laser irradiation condition for correcting a camber would possibly cause the crown to be outside the permissible range. Thus, the correction process should consider the relationship between them, and this makes the correction more difficult and the correction time longer.